Means por transforming mechanical vibrations into electrical



Feb. 13, 1923. Re. 15,540 I L. DE FOREST MEANS FOR TRANSFORMING MECHANICAL VIBRATIONS INTb ELECTRICAL VIBRATIONS Original Filed July 15, 1919 Reiesued Feb. '13.,1923. UNITED STATES.

PATE T-. F CE- LEE m; FOREST, on NEW YORK. N. Y,, ASSIGNOR To DE FOREST RADIo'TELErnoNE AND TELEGRAPH COMPANY,IOF NEW YORK, 1v. Y.,-A CORPORATION OE DELAWARE.

MEANS FOR TRANLSFOIQMING MECHANICAL VIBRATIONS III'I'O ELECTRICAL YIBRATIONS.

Original No. 1,309,753, dated July 15, 1919, Serial 1W0. 73,678, filed January 22. 1916. Application m reissue filed July 13, 1921. Serial NO.484,53'2. i

To all whom it may concern: I I I I Be it known that I, LE on FoREsT, a citizen-of the United States, residing at New.

York, county of Bronx, and *State of New 5 York, have made a certain new and useful Invention in Means for Transformi Mech'anical'vi'brations into ,Electrical ,ibrations, of which the'following is a specification..- w The invention relates to means for changin mechanical into electrical vibrations.

he object of the invention is to provide means which are simple and eflicient for chan ing mechanical vibrations into electrical v1 rations, and by mechanical vibrations" I mean vibrations created mechanically as distinguished from' vibrations created electrically or electro-magnetically.

A further object of theinvention is to accomplish the purposes above referred to 'by means of an evacuated vessel containing electrodes therein.

Further objects of. the invention will ap--- pear more fully hereinaften. I

The "nvention consists substantially 1n the construction, combination, location and rela- 'tive arrangement of parts andcircuit arrangements associated therewith, all as -w1ll be more fully hereinafterset forth,asshown by the accompanying drawing, and finally pointed out in the appended claims.

Referring to the'drawi'ng,-

Figure 1 .shows one circuit arrangement embodying my invention.

heated from suitable source, such as a bat-' ter A, controlled by resistance R. I

n the arrangement shownin Fig. 1, I prefer 'to form the filament electrode F,

coiled, as shown, and placed in a plane parallel to the plane of the plate electrode,

Fig. .2 shows a modiiied construction of the vessel employed in accordance w th my.

which in this instance is in the formof. a circular plate and is mounted on a. wire or conducting rod K sealed in one side of the vessel and extending and rigidly fastened to diaphragm D closing .a mouth piece designated at M. A flux source, suchas battery B, is connected 1) its negative termlnal to one side of the li lam ent F and by scribed, is I very simple. Sound waves through mouth piece M, impinge on the diaphragm D, and its to and fro vibration or its positive terminal through one coil P of 1 of the device thus de-' longitudinal motion is transmitted mechanically by ,means of the rod K to the plate electrode W,-there-by varying in accordance therewith the distance between the'plate electrode W and the cathode or filamentelectrode'F. These minute variations in 'the'TQ I, distance between the electrodes, cause cor-.1"

responding variations in '-the 'momentary amount of flux current from-source'B- pass-.

ing by ionic conductivity from the filament Fto the plate. W. They are then transmitted over thatelephone line L to the telephone receiver T, as will ,be readily under- StOO dQ I j, Y

thatthis arrangement. which is in substance a substitute for a'f microphone, is free from .most of the .im erfeotiOns of any mechanical resistance varying device such as are inherent tothe carbon granule microphone, and that in consequence a clearness and fidelity of sound\'reproduction is obtaind inthe telephone receiver far superior to t at possible when a microphone 1s employ 1 The magnitude of vibrations obtained in :the device shown in Fig.1, even when the vessel U is made of large diameter, and of thin glass, is not 'reat, and there is obviously a mechanical imit to the nearness with which the plate W, can be placed to the filament or cathode F, in order to insure against actual'conta'ct of the two electrodes. To, remedy this one objection I have found that the arrangement shown in Fig.

end the plate electrodeVV in close proximityto the filament F as hereinbefore described.

The long glass stem or neck C, is quite flexible and permits therefore, relatively large movements of the arm or rod K sealed therein. If desired, a metal support E may be fastened around the base of the neck C, as shown, provided with a'thumb screw G for slightly bending the glass neck, thereby alfording means for adjusting the position of the plate electrode W, relative to the filament F. l A piece of rubber, felt or other soft material designated at H, forming a tip for the screw G permits the glass neck to be vibrated slightly as impelled by the rod K, and at the same time it dampens any natural vibration of theneck C. It will be noticed that the circuit arrangement of this figure is identical to that of Fig. 1, and the principle of'operationthereof is the same.

In Fig. 3, I show a vessel U similar to that.

of Fig. 2, but I employ in connection there with two cold electrodes associated with the filament electrode F. In this arrangement the arm K terminates in a wire interposed between the filament electrode F, and the third electrode Y. The electrode Y is pref- -erably in the form of a plate, bent at an angle as shown, and is supported by a suitable rod J sealed into the vessel U and the plate is connected through a telephone transformer as shown in Figs 1 and 2, to the telephone T or direct thereto, and to the source B, and one terminal of the filament F all as shown. In this instance an electric charge, the amount and polarity of which is controlled by the potentiometer P, and battery B, connected to the filament F, and the arm K, is maintained on the vibrating member N. The operation oi? the device described is similar to the, operation of the arrangements shown in Figs. 1 and 2.

In Fig. 4:, I show an audion microphone similar to that shown in Figs. 1 and 4. The grid electrode N and the plate electrodejW, are connected to the filament F, through inductively associated coils S and P, respectively ofa regenerative'oscillating circuit. A tuning condenser C is shown connected around the coil P, and a stopping condenser C", shunted by a high resistance leak path R is connected in the grid circuit. In this arrangement I gefer to employ a direct cur rent generator for the source of the flux current in the circuit of which is inserted an impedance or choke coil I. G is a shunting capacity connected across the terminals of the generatoras shown. The output or loadcircuit is inductively or otherwise associated with one or both of the coils P and S through a third coil S.

By this arrangement the oscillating audion system becomes a generating source of undamped electrical oscillations suitable, for egrample, in ,a radio telephonetransmitting system. The amplitudes of these oscillations are modulated by the movements of th voice controlled electrode W. I

It is obvious that many other arrangements will readily occur to those skilled in the art without departing from the broad scope of my invention as defined in the claims.

Therefore, what I claim as new and useful and desire to secure by Letters Patent, is:

1. In a device of the class described, the combination with a source of mechanical vibrations, a vessel provided with a comparatively thin neck, electrodes sealed in said vessel, one of said electrodes extending through said neck and connected to said source, said mechanical vibrations causing corresponding vibrations of said neck and variations in an output circuit also nected to said electrodes.

2. In a device of the class described, the combinationwith a source of mechanical vibrations, a vessel provided with a comparatively thin neck, electrodes sealed in said vessel, one of said electrodes extending through said neck and connected to said source, said mechanical vibrations causing corresponding vibrations of said neck and variations in an output circuit also connected to said electrodes, and means for detecting the variationsof said output circuit.

3. In a device of the character described, a vessel comprising a body provided with a comparatively long thin neck, an electrode sealed in the neck of said vessel and extending into the body thereof, a second electrode in said vessel, said first electrode being capable ofmovement relative to said second electrode.

4. In a device of the character decribed, a vessel having a comparatively thin neck, electrodes sealed in said vessel, one of said electrodes extending through said neck, said neck and electrode being capable of vibration to cause variations in an output circuit connected with said electrodes.

ling the conductance thereof, an electric circuit including a source of electric current and the other to collect electrons, and a third the cathode and anode members, and electroelectrode movable with respect to said elecmagnetic mechanism controlled by the ci:rtrodes whereby the electron flow between 10. cuit substantially as described. said fixed electrodes may be varied.

5 8. In a device of the class described, two In-Wit-ness whereof, I hereunto subscribe electrodes fixed relative to each other, one my name, this 23d day of June, A. D., 1921. of said electrodes being'adapted to emit and LEE on FOREST. 

